Introduction to Bladder Care for People with Spinal Cord Injury
The urinary system includes the kidneys, ureters, bladder, sphincter muscles and 
the urethra. The purpose of the urinary system is to remove waste from the blood in the form of urine.
There are two kidneys, one on either side of the body. Blood flows to the kidneys and combines the waste and water to make urine. There is a ureter that connects each kidney to the bladder. It allows the urine to flow into the bladder. The bladder collects and holds the urine until it is time to urinate. It stretches when it is full and shrinks when it is empty.
The sphincters are two muscles in the bladder which close to keep the urine in the bladder as well as open to let the urine out of the bladder. The urethra is a muscular tube leading from the bladder to the outside of the body. This is the exit point for urine outside the body.
Normally (before the spinal cord injury), the bladder would empty (urination) when the brain sends messages through the spinal cord telling the bladder to contract so the sphincter muscles will open. When the sphincter opens, the bladder drains.
Process of Urination Before Spinal Cord Injury
1. The bladder stretches as it fills with urine.
2. This stretching pushes on area nerves.
3. The nerves send a message from the bladder to the spinal cord.
Part of the message loops around in the cord, setting off a reflex, which causes the bladder to contract. The other part of the message goes to the brain. The "urge" (sensation/feeling) to urinate is felt.
4. At this point, the brain decides if it is an acceptable time to urinate.
5. If it is not a good time to urinate, the brain sends a message back down the cord to tell the sphincters to stay closed and keep the urine in the bladder.
6. If it is a good time to urinate, the brain sends a message back down the cord to tell the sphincters to open and let the urine exit the body.
